[clang-tools-extra] [clangd] Use TargetOpts from preamble when building ASTs (PR #88381)

[Ilya Biryukov via cfe-commits]

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@@ -451,6 +451,7 @@ ParsedAST::build(llvm::StringRef Filename, const ParseInputs &Inputs,
   DiagnosticConsumer *DiagConsumer = &ASTDiags;
   IgnoreDiagnostics DropDiags;
   if (Preamble) {
+    CI->TargetOpts = Preamble->TargetOpts;
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ilya-biryukov wrote:

It'd be useful to add a comment here explaining why we need it (i.e. "workaround a crash, see ParsedASTTest.PreambleWithDifferentTarget")

https://github.com/llvm/llvm-project/pull/88381